Back in 2010 when I was drawing Magnus Robot Fighter I was working on pages with large cityscapes so I put together in Photoshop a rough collage of both photography and sci-fi illustration that I like in order to experiment with depth and scale of a multi-level city.

Yes, Metropolis is of course the source that influenced so much more afterwards. Jean Giraud (Moebius) has done very influential work like this and along with and Jean-Claude Mézières they both did design work on The Fifth Element.Then of course there is also Roy Krenkel and Al Williamson.